1. Field of the invention
The invention concerns a gasifier reactor internal coating.
2. Description of the Prior Art
There is known in the art in particular a gasifier used to gasify coal. The coal gasification process, that has been known in the art for around fifty years, is currently experiencing strong growth because it can be used, starting from highly diverse hydrocarbon materials, for example coal, petroleum coke, and even heavy oils to be recycled, to produce synthesis gases serving as an energy source and as basic compounds for the chemical industry. This process also eliminates unwanted components, for example NOx, sulfur or mercury, before discharge into the atmosphere.
The principle of gasification consists in controlled partial combustion, under pressure and in a steam or oxygen atmosphere, at a temperature from approximately 1000° C. to approximately 1600° C.
There exist different types of reactor, known as “gasifiers”, with fixed, fluidized or driven beds. These reactors differ in the mode of introduction of the reactants, the manner in which the fuel and the oxidizer are mixed, the temperature and pressure conditions, and the method of evacuating liquid residual slag or ash resulting from the reaction.
The article “Refractories for Gasification” published in the journal “Refractories Applications and News”, Volume 8, Number 4, July-August 2003, written by Wade Taber of the Energy Systems department of the Saint-Gobain Industrial Ceramics Division, describes the structure of a gasifier internal coating. The gasifier is coated with various layers of refractory products capable of withstanding the conditions of temperature, pressure and chemical environment to which they are subjected during gasification. The layers of refractory products thus protect the metal interior wall of the gasifier from heat and from corrosion by gases and slag.
The refractory product at the hot face is more particularly subjected to erosion and chemical attack by ash or slag, which leads to the infiltration of compounds from the liquefied ash or slag into the pores of the refractory product. As a result of erosion and thermal cycling, this infiltration can cause spalling of the coating, and finally to shutting down of the reactor.
To increase the service life of refractory coatings, researchers have attempted to increase their thickness. However, this solution has the drawback of reducing the usable volume of the gasifier and therefore its yield.
James P. Bennett, in the article “Refractory liner used in slagging gasifiers” published in the journal “Refractories Applications and News”, Vol 9, Number 5, September/October 2004, pages 20-25, explains that the service life of current gasifier refractory coatings, in particular in air-cooled systems, is very limited despite their high content of chromium oxide. He mentions in particular the report by S. J. Clayton, G. J. Stiegel and J. G. Wimer “Gasification Technologies, Gasification Markets and Technologies—Present and future, an Industry Perspective”, US DOE report DOE/FE 0447, July 2002.
There is therefore a requirement for a refractory coating adapted to resist the corrosion encountered in gasifiers more effectively and more durably than prior art products.
The object of the invention is to satisfy this requirement.